Problem: $\sum\limits_{x=1}^{3 }{{(4x)}}=$
Solution: What is the question asking for? $\sum$ tells us to find the sum. The question is asking for the sum of the values of $4x$ from $x = 1$ to $x = 3$. Evaluating $\begin{aligned} \sum\limits_{x=1}^{3 }{({4x})}&= (4(1)) + (4(2)) + (4(3)) \\\\ &= 4 + 8 + 12 \\\\ &= 24\end{aligned}$ The answer $\sum\limits_{x=1}^{3 }{({4x})}=24$